1. Field of the Invention
This invention relates to computers and memory storage systems. More particularly, this invention relates to memory storage systems having swappable elements.
2. Previous Art
Typically a host system such as a computer system will have at least one data bus capable of communicating digital signals between a processor and a memory storage device. Often single data buses serially connect with numerous memory storage devices such as is common in systems which employs SCSI architecture. SCSI is an acronym for small computer standard interface.
Increased data storage capacity and through-put are demanded in the marketplace. This demand has driven the development of computer systems with multiple data buses. Multiple buses provide a wider channel for communicating data through than a single bus may provide. The wider channel provided with serial computer subsystems enables more rapid through-put. The wider channel enables increased storage capacity in memory storage systems by enabling increasing numbers of memory storage devices to be connected with the channel.
Multiple memory storage devices have been arranged in an array to increase data storage capacity. The array communicates with the host system bus so that the host system may simultaneously communicate with multiple memory storage devices. Various computer systems have hundreds of discrete memory storage devices arranged in arrays to achieve hundreds, and even thousands, of gigabytes of memory storage capacity.
Data reliability in memory storage systems is important. The more memory storage devices which operate in a system, the higher the likelihood one will fail. If a single memory storage device fails, data may be lost. In order to increase data reliability, redundancy between memory storage devices may be introduced such as in a RAID system. RAID is an acronym for "Redundant Array of Independent Disks".
RAID systems typically rely on a device controller (e.g. RAID controller) to regulate the operation of memory storage devices such as hard disk drives, in an array. The device controller, while often appearing to the host system as a single memory storage device, may regulate multiple memory storage devices. For example, a device controller may employ data storage methods including data striping and parity across numerous memory storage devices.
To improve host system reliability by reducing the probability of down time, storage systems having redundant controllers have been introduced. With redundant controllers, when one controller fails another controller assumes the role of the failed controller to provide continuity of operation of the memory storage system. The failed controller may then be swapped with a new controller when the host system is shut down for maintenance.
Several problems exist with systems having redundant device controllers. The physical location of a failed device controller may be difficult or virtually impossible to identify. Often the host system must often be shut down to facilitate replacement of a failed device controller. Replacement of a single device controller may require disconnection of multiple buses and other connectors as well as removal of numerous fasteners. These problems are sought to be overcome.
Generally, when a device controller fails, the host system will typically alert a system administrator or technician through a message displayed on the system administrators computer screen. The message may identify the failed device controller by a SCSI ID numeral and a bus ID numeral. The physical location of the failed device controller is generally not available.
Identification of the physical of location of a failed device controller may require removal and testing of each device controller in a system until the failed controller is found. Removal of the wrong controller can cause failure of multiple memory storage devices and loss of data. What is desired is a way to readily identify the physical location of a device controller such as a failed device controller ease replacement of the device controller.
Replacement of a device controller may be a time consuming and multi-step process. To illustrate, an example of a known device controller is shown in FIG. 4. The device controller in FIG. 4 includes multiple data ports. The multiple data ports are capable of various connections. The various connections include connection with host data buses, memory storage device buses, a power cable, a serial interface and fault signal buses, for example. Each bus must be removed and reconnected to facilitate replacement of the controller.
The replacement of a device controller having multiple data ports may take hours to complete. Additionally, there is a possibility that the buses may be incorrectly connected. What is desired is a simple way to interconnect device controllers with a memory storage system.
Host system downtime is undesirable. Replacement of a failed device controller often causes memory storage system and/or host system downtime. What is desired is a way of replacing a failed device controller without host and/or memory storage system downtime.